How to retrieve $('input:radio[name=vote]:checked').val()

How to retrieve $('input:radio[name=vote]:checked').val()

Hello,
This is my issue:
I've got a simple poll
  1. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title></title>
    <link rel="stylesheet" type="text/css" href="style.css?" />
    <script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
    <script type="text/javascript">
        $(document).ready(function(){
            $("#poll #submit").click(function () {
                $("#poll").html('<img src="ajax-loader.gif" />');
                $.ajax({
                    type: "GET",
                    data: "data=" + $('input:radio[name=vote]:checked').val(),
                    url: "response.php",
                    success: function(msg){
                        $("#poll").html(msg)
                    }
                });
            });
        });
    </script>
    </head>

    <body>
     <div id="poll">
                    <h4>Here comes the question...?</h4>
                   
                    <div class="label">               
                    <input type="radio" name="vote" value="0"  />
                    <label for="vote">Answer 1:</label>
                    </div>
                    <br />
                    <div class="label">
                    <input type="radio" name="vote" value="1"  />
                    <label for="vote">Answer 2:</label>               
                    </div>
                    <input type="button" name="submit" value="Vote" id="submit" />
                   
                   
        </div><!-- end poll -->


    </body></html>










































response.php
  1. <?php
        $sampleData = $_GET['data'];
       echo $sampleData; ?>

but at the and I get "undefined" as returned value, instead of  values of radio buttons "0" or "1" which I should.
I found $('input:radio[name=vote]:checked').val() should be the correct code to retrieve the values of radio inputs, but in my case doesn't work ,or I am doing something wrong?